Method and arrangement for cleaning and controlling tube-type heat-exchangers



May 16, Wm? H. NASSEZ 3,319,766!

METHOD AND ARRANGEMENT FOR CLEANING AND CONTROLLING TUBE-TYPE HEAT-EXCHANGERS Filed Feb. 1, 1955 HEAT HEAT HEAT T EXCHANGER *1 EXCHANGER *1! f EXCHANGER v F. I

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United States Patent Office fidil h'lhi Patented May 16, 1967 3,319,704 METHGD AND ARRANGEMENT FBR CLEANING AND CONTRGLLING TUBE-TYPE HEAT-EX- (STRANGERS Hans Nasse, Angermund, Germany, assignor to Ludwig Taprogge-Reinigungsanlagen fur- Rohren-Warmeaustauscher, Angermund, Germany Filed Feb. 1, 1965, Ser. No. 429,244 Claims priority, application Germany, Feb. 18, 1964, T 27,881 15 Claims. (Cl. 165-1) This invention relates to an apparatus for self-cleaning heat-exchangers of the pipe or tube-type, i.e., in which transfer of heat is effected between two media, one of these media being conveyed through sets of pipes or tubes connected in parallel and the other media passing through the space between these tubes.

Since the present invention affords great advantages especially in the use of controllable tube heat exchangers primarily this type of heat exchanger is referred to in the following description. It is, however, understood that the present invention is not restricted to use with this type of heat exchanger but may be used advantageously with all other kinds of heat exchangers of the pipe or tubetype.

As is known to all persons skilled in the art, the efficiency of a heat exchanger of the pipe or tube-type is unavoidably lessened after a certain time of operation due to deposits which form along the inner tube walls. Such deposits are caused by mechanical impurities carried with the media, such as cooling water passing through the pipes or tubes and/ or by substances contained in this media in a state of solution but precipitated therefrom by thermal and/ or chemical influences. These deposits impede the heat transition or transfer through the pipe or tube walls and thereby deteriorate the efficiency of the heat exchanger. When this efliciency is lowered to a certain fraction of the original efiiciency thereof, the tubes or pipes must be cleaned to restore the original efficiency.

For purposes of cleaning heat-exchangers, especially condensers of power plants and the like, a method of cleaning the condenser pipes is known in the prior art in which cleaning bodies, preferably elastic cleaning bodies, having the specific weight of the cooling water are added to the cooling water and are guided together with and carried by the cooling water through the condenser pipes. The elastic cleaning bodies serve as friction members which scrape the inner tube walls as they pass through the condenser pipes. From the outlet of the condenser the cooling water passes through a sieve installation which intercepts the cleaning bodies and returns them by way of connecting lines between the cooling water inlet and the cooling water outlet to the inlet pipe to the condenser. The U.S. Patents Nos. 2,801,824 and 3,021,117 to L. Taprogge are representative of such prior art arrangernents.

Cleaning of small tube heat-exchangers as they are used in groups of formations in the chemical industry, paper factories, power plants, etc., is generally not possible without impairment of all or a substantial part of the operation of the heat exchangers unless cleaning is effected in accordance with the above-mentioned continuous cleaning operation. However, the use of this known method presupposes that a suifi-cient pressure gradient exists along the heat-exchanger tubes in order to assure good transportation of the friction members through the tubes. This pressure gradient cannot be produced arbitrarily since with decreasing size of the friction members in relation to the inside diameter of the tubes and with diminishing contact pressure of the friction members against the inner wall of the tube, the friction effect also diminishes resulting in a reduction in the efficiency of the cleaning operation. A minimum pressure gradient is, however, fulfilled only in rare cases in practice with such heat-exchangers, because the heat-exchangers are often over-dimensioned and are operated with the flow volume of the heat-exchange media greatly dependent upon the degree of fouling of the heat transfer surfaces. In other cases, the control of the heat transfer function is accomplished by selective throttling of the flow media whereby a broad regulating range must be anticipated.

In still other cases, a plurality of heat-exchangers are combined into a common circuit, the supply pressure of which is not suflicient to obtain the required minimum pressure gradient throughout the system. Aside from purely technical difiiculties, the known continuous cleaning method for reason of cost, has not been utilized in multiple heat exchange systems inasmuch as it was thought that each individual heat-exchanger would require a separate separation device and return pump. On the other hand, a continuous cleaning of the heat-exchanger is not necessary in most cases since periodic cleaning is often sufiicient to avoid impairment of efficient operation.

Therefore, the invention provides a method of and apparatus for the cleaning of controlled tube he-at-exchangers by means of friction members carried through the system during continuous operation of the heat-exchangers, even when, for operational reasons, extensive regulation of the heat-exchanger through wide variation of the flow volume of the heat-exchanger media is called upon. Additionally, the possibility should exist to ac complish the method in such a manner, that cleaning of a number of heat-exchangers is possible with one cleaning arrangement.

The invention relates to a method for cleaning of controlled tube heat-exchangers by means of friction members guided in the system which, due to the pressure gradient of the heat-exchange media along the heat-exchanger tubes are pushed through the tubes. The invention consists therein, that an essentially constant flow of heat-exchange media is fed to the heat-exchanger at all times independent of the control status which is required to push the friction members through the heat-exchanger tubes or is necessary for maximum of heat transport; however, in dependence on the required control status a greater or lesser share of the flow volume without exchange of heat and together with the friction members in the circuit is returned to the inlet of the heat exchanger.

The invention is based upon the principle that it is possible by returning a part of the flow media from the heat exchanger directly to the inlet of the heat-exchanger to continuously change the temperature level there in such a manner that the exchange of heat is controlled without appreciably changing the quantity of heat-transfer media passing through the heat-exchanger. In this way the quantities which circulate in the circuit, that is, the quantities made available by the heat-exchange media source,

' change only in accordance with the control status of the heat-exchanger. This results therein, that independent of the control status, an essentially equal pressure gradient is maintained at all times along the heat-exchanger tubes.

The invention provides for a heat-exchanger connected in the direction of flow of the heat-exchange media in series with a pressure pump, a separating device, known per se, for collecting the friction members and a regulating valve connected to the heat-exchange source. The

arrangement is further provided with a return line connecting the separating device with the inlet of the heatexchanger. Naturally, within the framework of the invention, it is also possible to arrange the pressure pump,

7 viewed in the direction of flow of the heat-exchange media, ahead of the heat-exchanger but behind the entrance of the return line. In case of a multiple heatexchanger combination, the heat-exchangers may be arranged directly in parallel so that the portion of heatexchange media flowing through the circuit may be returned through a single return line. According to the basic thought of the invention, the pressure pump is such, that it produces tthe full pressure gradient required to push the friction members through the heat-exchanger tubes, or dependent upon which has the larger requirements, produces that quantity required for the proper transsport of heat.

In case of a multitude of heat-exchangers arranged in parallel, the pump is to be designed for the requirements of the single heat-exchanger which requires the largest quantity of heat-exchange media, whether it is for the transport of heat or for the production of the necessary pressure gradient. A cleaning system is then provided in parallel to the working media circuit to which that heatexchanger requiring cleaning at any given time may be connected during short cleaning periods by means of appropriate valves or reverse valves without disrupting the operation of the heat-exchanger. In case a control for the dirty heat-exchanger is provided, the control impulse must be switched from the regulating valve associated with it to the common control valve of the cleaning circuit.

The invention allows in an advantageous way for the cleaning of controlled heat-exchangers by means of friction members guided in the circuit during operation of the heat-exchanger also, if for operational reasons, the control of the heat-exchanger is accomplished by altering the flow quantity supplied from the heat-exchange source. Particularly, cleaning of a multitude of heat-exchangers arranged in parallel is possible with only one cleaning unit without materially increased costs.

Accordingly, it is an object of the present invention to provide a method and control arrangement for use with self-cleaning heat-exchanger installations which eliminates, by simple means and in an effective manner, the aforementioned disadvantages and shortcomings encountered with the prior art constructions.

It is another object of the present invention to provide a method for controlling tube-type heat exchangers having self-cleaning installations while maintaining a substantially constant pressure gradient in the heat exchanger unit.

Still another object of the instant invention resides in the provision of a method of and arrangement for the cleaning of controlled tube heat exchangers by means of friction members carried through the system during continuous operation even when extensive regulation of the heat exchanger is required.

Still a further object of the present invention resides in the provision of a method of and arrangement for the cleaning of a heat exchanger system including a plurality of heat exchanger units by means of a single cleaning apparatus.

Another object of the present invention resides in the provision of a self-cleaning heat-exchanger system in which sole control thereof is effected in response to selected feedback of heat exchange fluid while a sufficiently constant pressure gradient is maintained at all times to insure proper transport of cleaning elements through the heat exchanger unit for all control requirements.

These and other objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein:

FIGURE 1 shows a schematic arrangement of an inventive heat-exchange system for accomplishing the inventive method for a single heat-exchanger;

FIGURE 2 shows a schematic arrangement of a modified system similar to that illustrated in FIGURE 1;

FIGURE 3 shows a schematic arrangement of an inventive heat-exchange plant for accomplishing the inventive method for a parallel combination of heat-exchangers; and

FIGURE 4 shows a schematic arrangement of an inventive heat-exchange plant for accomplishing the inventive method for a number of parallel heat-exchangers.

In the exemplified embodiment illustrated in FIGURE 1, a heat-exchanger 1 is connected in series with a constant flow pressure pump 2, a known separating device 3, such as disclosed in the above-referenced Taprogge patents, for collecting the friction members and a regulating valve 4 and connections 6, 7 to the source for the heat-exchange media, not shown. Additionally, a return line 5 is provided which connects the separating device 3 with the inlet of the heat-exchanger. The separating device 3 serves for the separation of the friction members from the heatexchange media volume which flows through the regulating valve and may, for example, consist of a funnelshaped screen incorporated into the line or a slanted screen or rack in the lowest point of which the return line 5 is arranged. As shown in FIGURE 2, the pressure pump 2 may also be arranged, in the direction of flow of the heat-exchanger media, ahead of the heat-exchanger and behind the inlet of the return line 5.

According to the basic idea of the invention, the pressure pump 2 is designed to constantly provide the full production of the pressure gradient required to push the friction members through the heat-exchanger tubes or to a level somewhat larger than the flow volume required for maximum heat transport. Independent from the control status of the heat-exchanger 1, essentially the same flow volume flows through the heat-exchanger tubes at all times due to the constant flow properties of pump 2. A more or lesser share of this flow volume, dependent on the control status, is passed through the circuit through the separating device 3 and return line 5 together with the friction members, whereas, the remaining share flows to the source of the heat-exchange media by way of the regulating valve 4 to thereby perform the exchange of heat. The ratio of both shares may be changed or altered separately by the regulating valve 4. A counterflow in the return line 5 from the inlet to the heat-exchanger (respectively the pressure pump 2) into the separative device 3 is only then possible when the pressure pump 2 is dimensioned too small. The pressure pump must, aside from the volume of the heat-exchange media required for maximum heat transport, also be provided for the transportation of the friction members through the return line from the separating device to the entrance of the heat-exchanger even during required maximum exchange of heat.

In the exemplified embodiment illustrated in FIGURE 3, two parallelly connected heat exchangers 1 are connected in series with a pressure pump 2, a known separating device 3 for collecting the friction members and a regulating valve 4 which is in turn connected to the source not shown of the heat exchange media via lines 6 and 7. Additionally, a return line 5 is provided which connects the separating device 3 with the inlet of the heat exchanger. Two heat exchangers 1 are connected directly in parallel, however, with such a combination it is obvious that the arrangement is not restricted to only two heat exchangers, but may include a larger number. According to the basic idea of the invention, the pressure pump 2 is designed for the full generation of the pressure gradient required to push the friction members through the heat exchanger tubes. Independent of the control status of the heat exchanger 1, essentially the same flow volume flows through the heat exchanger tubes at all times; however a more or lesser share of this flow volume, dependent on the control status, is passed from the separating device 3 through return line 5, whereas, the remaining share flows to the source of the heat exchange media by way of the regulating valve 4 thereby to perform the exchange of heat. The ratio of both shares is changed or altered separately by the regulating valve 4, which selectively controls the amount of flow through pipe 7. A counter flow in the return line 5 between separating device 3 and the entrance to the heat exchangers 1 is only possible, when the pressure pump 2 is designed too small. Additionally, in designing the pressure pump 2, care must be taken that even with maximum exchange of heat, a sufficient quantity of heat exchange media is available in order to transport the friction members from the separating device 3 through the return line 5 to the entrance of the heat exchangers 1.

In the exemplified embodiment illustrated in FIGURE 4, the two outer heat-exchangers 1a and 1c are connected in parallel to the operating media circuit via lines 6 and '7 through three way valves 8a, 80, 9a and fie, whereby the exchange of heat for each heat-exchanger is controlled separately through regulation of the flow volume by means of valves 16a and 100 which are in turn regulated by control impulses for the respective heat exchangers in the conventional manner, for example. The middle heatexchanger 1b is, with the position of the three Way valves 8b and 9b as illustrated, connected to the cleaning circuit as provided. The friction members flow, together with the circulating volume which is essentially always the same, from the separating device 3 through the pressure line of the cleaning circuit through the three way valve 8b into the heat-exchanger lb and after cleaning of the tubes from here through the drain pipe of the cleaning circuit to the pressure pump 2 and the separating device 3. The more or lesser volume of the heat-exchange media required for transporting the heat and controlled by the position of the regulating valve 4, flows from the pressure line of the operating circuit through the three way valve 8 to the heat-exchanger 1 and from here further through the drain line of the cleaning circuit, the pressure pump 2, the separating device 3, and the regulating valve 4 into the drain line 7 of the heat-exchange media circuit. The regulating valve 4 of the cleaning circuit receives the control impulse through switch means 11 in parallel or series connection to the regulating valve Irila, Iltlb or 10c assigned to the heat-exchanger to be cleaned. The switch means 11 may be a conventional manually operated selector switch, as illustrated, which merely applies the control impulses provided at the primary valve 10a, 16b or 100 to the valve 4 during the time that flow is diverted therefrom through the valve 4 from a given heat exchanger unit. Of course, the switch means 11 may also be operated in conjunction with the valves 8 and 9 to provide automatic control. thereof in any conventional manner. Thus, the valves 8 and 9 along with the switch means 11 serve as means for selectively connecting a single heat exchanger unit to the cleaning circuit while switching control over that heat exchanger from the associated valve 10 to the valve 4. In the exemplified embodiment illustrated in FIGURE 2, the pressure pump is arranged behind the heat-exchanger relative to the direction of flow. Naturally, the same effect is also possible with the pump ahead of the heat-exchanger when viewed in the direction of flow. L

While we have shown and described several embodiments in accordance With the present invention, it is understood that the same is not limited thereto but is sus ceptible ofv many changes and modifications within the spirit and scope thereof, as known to a person skilled in the art, and we, therefore, do not wish to be limited to the details shown and described herein, but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

Iclaim:

1. A method of cleaning and controlling a heat exchanger system having a source of heat exchange fluid, at least one tube-type heat exchanger unit and means for applying a heat exchange fluid containing a plurality of rubbing elements thereto, the method comprising dividing the heat exchanger fluid flowing from said heat exchanger unit into a first portion including said rubbing elements and a second portion free of rubbing elements,

conveying said first portion of said heat exchange fluid directly to the input of said heat exchanger unit, applying said second portion to said source of heat exchange fluid and while maintaining a constant pressure gradient in said heat exchanger unit varying the proportion of said first portion with respect to said second portion in accordance with the instantaneous control status required by said heat exchanger unit.

2. Method of cleaning and controlling a heat exchanger system having a source of heat exchange fluid, at least one tube-type heat exchanger unit and means for applying a heat exchange fluid containing a plurality of rubbing ele ments thereto, the method comprising dividing the heat exchange fluid flowing from said heat exchanger unit into a first portion including said rubbing elements and a second portion free of rubbing elements,

conveying said first portion of said heat exchange fluid directly to the input of said heat exchanger unit, applying said second portion to said source of heat exchange fluid, and

while maintaining a constant pressure gradient in said heat exchanger unit, varying the proportion of said first portion with respect to said second portion in accordance with the instantaneous control status required by said heat exchanger unit, the pressure maintained in said heat exchanger unit being such that under conditions of said proportion being a. minimum, suflicient heat exchange fluid is provided in said first portion to carry said rubbing elements through said system.

3. Method of cleaning and controlling a heat exchanger system having a source of heat exchange fluid, at least one tube-type heat exchanger unit and means for applying said heat exchange fluid thereto, the method comprising dividing the heat exchange fluid flowing from said heat exchanger unit into a first portion and a second portion,

conveying said first portion of said heat exchange fluid directly to the input of said heat exchanger unit, applying said second portion to said source of heat exchange fluid and while maintaining a constant pressure gradient in said heat exchanger unit varying the proportion of said first portion with respect to said second portion in accordance with the instantaneous control status required by said heat exchanger unit.

4. A heat-exchanger system having a continuous selfcleaning installation comprising a source of heat exchange fluid in part containing a plurality of rubbing elements,

at least one tube-type heat-exchanger unit,

, an inlet conduit connected with said source of heat exchange fluid and said unit for conducting said heat exchange fluid containing a plurality of rubbing elements thereto,

an outlet conduit connected with said unit,

rubbing element separating means and regulating valve means connected in series in the direction of flow of said heat exchange fluid in said outlet conduit between said unit and said source of heat exchange fluid, and fluid return line means connected between said separating means and said inlet conduit for convying a portion of said heat exchange fluid containing said rubbing elements directly to said heat exchanger unit, said regulating valve means selectively controlling the proportion of heat exchange fluid carried directly to said inlet conduit as opposed to that returned to said source, constant flow pressure pump means connected to said heat exchanger unit between said fluid return line means and the heat exchanger unit providing an essentially constant pressure gradient at all times within said heat-exchanger unit.

5. A heat-exchanger system having a continuous selfcleaning installation comprising a source of heat exchange fluid in part containing a plurality of rubbing elements,

at least one tube-type heat-exchanger unit,

an inlet conduit connected with said source of heat exchange fluid and said unit for conducting said heat exchange fluid containing a plurality of rubbing elements thereto,

an outlet conduit connected with said unit,

rubbing element separating means and regulating valve means connected in series in the direction of flow of said heat exchange fluid in said outlet conduit between said unit and said source of heat exchange fluid, and fluid return line means connected between said separating means and said inlet conduit for conveying a portion of said heat exchange fluid containing said rubbing elements directly to said heat exchanger unit,

said regulating valve means selectively controlling the proportion of heat exchange fluid carried directly to said inlet conduit as opposed to that returned to said source,

constant flow pressure pump means connected to said heat exchanger unit providing an essentially constant pressure gradient at all times within said heat-exchanger unit,

said pressure pump means being connected between said outlet conduit and said rubbing element separating means.

6. A heat-exchanger system having a continuous selfcleaning installation comprising a source of heat exchange fluid in part containing a plurality of rubbing elements,

at least one tube-type heat-exchanger unit,

an inlet conduit connected with said source of heat exchange fluid and said unit for conducting said heat exchange fluid containing a plurality of rubbing elements thereto, an outlet conduit connected with said unit, rubbing element separating means and regulating valve means connected in series in the direction of flow of said heat exchange fluid in said outlet conduit between said unit and said source of heat exchange fluid, and fluid return line means connected between said separating means and said inlet conduit for conveying a portion of said heat exchange fluid containing said rubbing elements directly to said heat exchanger unit,

said regulating valve means selectively controlling the proportion of heat exchange fluid carried directly to said inlet conduit as opposed to that returned to said source,

constant flow pressure pump means connected to said heat exchanger unit providing an essentially constant pressure gradient at all times within said heat-exchanger unit,

said pressure pump means being connected to said inlet conduit between said heat-exchanger unit and the connection of said fluid return line means. 7. A heat-exchanger system having a continuous selfcleaning installation comprising at least one tube-type heat exchanger unit having an inlet conduit and an out-let conduit each connected to a source of heat exchange fluid,

separating means connected between said outlet conduit and the fluid source for diverting a portion of the exchange fluid from said outlet conduit,

return line means connecting said separating means to said inlet conduit for conveying said portion of said heat exchange fluid directly to said heat exchanger unit,

means providing the sole control of saidheat-exchanger system for selectively controlling the amount of the portion of heat exchange fluid carried by said return line means directly to said inlet conduit, and constant flow pressure pump means connected between said return line means and said heat exchanger unit providing an essentially constant pressure gradient at all times within said heat exchanger unit. 8. A heat-exchanger system having a continuous selfcleaning installation comprising at least one tube-type heat exchanger unit having an inlet conduit and an outlet conduit each connected to a source of heat exchange fluid, separating means connected between said outlet conduit and the fluid source for diverting a portion of the exchange fluid from said outlet conduit, return line means connecting said separating means to said inlet conduit for conveying said portion of said heat exchange fluid directly to said heat exchanger unit, means providing the sole control of said heat-exchanger system for selectively controlling the amount of the portion of heat exchange fluid carried by said return line means directly to said inlet conduit, and constant flow pressure pump means providing an essentially constant pressure gradient at all times within said heat exchanger unit, said pressure pump means being connected between said outlet conduit and said separating means. 9. A heat-exchanger system having a continuous selfcleaning installation comprising a source of heat exchange fluid, .a plurality of tube-type heat exchanger units connected in parallel to said fluid source, inlet and outlet conduit means connecting each of said units to said fluid source, regulating valve means connected between each outlet conduit means and said fluid source for regulating the flow of heat exchange fluid in each unit, cleaning circuit means having heat exchange fluid containing a plurality of rubbing elements, constant flow pump means, separating means for said rubbing elements and additional regulating valve means, said separating means having a discharge line for said rubbing elements and an output line connected to said fluid source for heat exchange fluid free from rubbing elements, and means for selectively connecting a single heat-exchanger unit to said cleaning circuit means including means diverting the fluid flow from the regulating valve means associated with that unit to said additional regulating valve means, said additional regulating valve means providing the sole control of the heat-exchanger unit connected to said cleaning circuit means for selectively controlling the proportion of heat exchange fluid carried by said discharge line and said output line. 10. A heat-exchanger system having a continuous selfcleaning installation comprising .a source of heat exchange fluid, a plurality of tube-type heat exchanger units connected in parallel to said fluid source, inlet and outlet conduit means and connecting each of said units to said fluid source, regulating valve means connected between each outlet conduit means and said fluid source for regulating the flow of heat exchange fluid in each unit, cleaning circuit means having heat exchange fluid cont aining a plurality of rubbing elements, constant flow pump means, separating means for said rubbing elements and additional regulating valve means, said separating means having a discharge line for said rubbing elements and an output line connected to said fluid source for heat exchange fluid free from rubbing elements, and means for selectively connecting a single heat-exchanger unit to said cleaning circuit means including means diverting the fluid flow from the regulating valve means associated with that unit to said additional regulating valve means, said additional regulating valve means providing the sole control of the heat exchanger unit connected to said cleaning circuit means for selectively controlling the proportion of heat exchange fluid carried by said discharge line and said output line, said means for selectively connecting a single heat exchanger unit to said cleaning circuit means including means capable of selectively connecting each inlet conduit means both to said fluid source and said cleaning circuit means. 11. A heat-exchanger system having a continuous selfcleaning installation comprising a source of heat exchange fluid, a plurality of tube-type heat exchanger units connected in parallel to said fluid source, inlet and outlet conduit means connecting each of said units to said fluid source, regulating valve means connected between each outlet conduit means and said fluid source for regulating the flow of heat exchange fluid in each unit, cleaning circuit means having heat exchange fluid containing a plurality of rubbing elements, constant flow pump means, separating means for said rubbing elements and additional regulating valve means, said separating means having a discharge line for said rubbing elements and an output line connected to said fluid source for heat exchange fluid free from rubbing elements, and means for selectively connecting a single heatexchanger unit to said cleaning circuit means while diverting flow from the regulating valve means associated with that unit, said additional regulating valve means providing the sole control of the heat exchanger unit connected to said cleaning circuit means for selectively controlling the proportion of heat exchange fluid carried by said discharge line and said output line, said means for selectively connecting a single heat exchanger unit to said cleaning circuit means further including means capable of selectively switching the control impulse from said regulating valve means associated with said single heat exchanger unit to said additional regulating valve means. 12. A heat-exchanger system having a continuous selfcleaning installation comprising a source of heat exchange fluid, a plurality of tube-type heat exchanger units connected in parallel to said fluid source, and cleaning circuit means having heat exchange fluid containing a plurality of rubbing elements, means for separating said heat exchange fluid into one part containing rubbing elements and a second part free from rubbing elements and regulating valve means for determining the quantitative ratio of said one part to said second part, and means for selectively connecting a single one of said heat exchanger units to said cleaning circuit means. 13. A heat exchanger system having a continuous selfcleaning installation comprising a source of heat exchange fluid, a plurality of tube-type heat exchanger units connected in parallel to said fluid source, and

cleaning circuit means having heat exchange fluid containing a plurality of rubbing elements, means for separating said heat exchange fluid into one part containing rubbing elements and a second part free from 5 rubbing elements and regulating valve means for determining the quantitative ratio of said one part to said second part, and means for selectively connecting a single one of said heat exchanger units to said cleaning circuit means, the input of said separating means being connected to the output of said one heat exchanger with the one part of said heat exchanger fluid being applied to the input of said one heat exchanger and the second part of said heat exchanger fluid being applied to said fluid source.

14. A heat exchanger system having a continuous selfcleaning installation comprising a source of heat exchange fluid, a plurality of tube-type heat exchanger units connected in parallel to said fluid source, and cleaning circuit means having heat exchange fluid containing a plurality of rubbing elements, means for separating said heat exchange fluid into one part containing rubbing elements and a second part free from rubbing elements and regulating valve means for determining the quantitative ratio of said one part to said second part, and means for selectively connecting a single one of said heat exchanger units to said cleaning circuit means, the input of said separating means being connected to the output of said one heat exchanger with the one part of said heat exchange fluid being applied to the input of said one heat exchanger and the second part of said heat exchange fluid being applied to said fluid source, said cleaning circuit means further including a constant flow pump means. 15. A heat exchanger system having a continuous selfcleaning installation comprising a source of heat exchange fluid, a plurality of tube-type heat exchanger units connected in parallel to said fluid source, and cleaning circuit means having heat exchange fluid containing a plurality of rubbing elements, means for separating said heat exchange fluid into one part containing rubbing elements and a second part free from rubbing elements and regulating valve means for determining the quantitative ratio of said one part to said second part, and means for selectively connecting a single one of said heat exchanger units to said cleaning circuit means, said cleaning circuit means further including a constant flow pump means.

References Cited by the Examiner UNITED STATES PATENTS ROBERT A. OLEARY, Primary Examiner N. R. WILSON, A. W. DAVIS, Assistant Examiners. 

1. A METHOD OF CLEANING AND CONTROLLING A HEAT EXCHANGER SYSTEM HAVING A SOURCE OF HEAT EXCHANGE FLUID, AT LEAST ONE TUBE-TYPE HEAT EXCHANGER UNIT AND MEANS FOR APPLYING A HEAT EXCHANGE FLUID CONTAINING A PLURALITY OF RUBBING ELEMENTS THERETO, THE METHOD COMPRISING DIVIDING THE HEAT EXCHANGER FLUID FLOWING FROM SAID HEAT EXCHANGER UNIT INTO A FIRST PORTION INCLUDING SAID RUBBING ELEMENTS AND A SECOND PORTION FREE OF RUBBING ELEMENTS, CONVEYING SAID FIRST PORTION OF SAID HEAT EXCHANGE FLUID DIRECTLY TO THE INPUT OF SAID HEAT EXCHANGER UNIT, APPLYING SAID SECOND PORTION TO SAID SOURCE OF HEAT EXCHANGE FLUID AND WHILE MAINTAINING A CONSTANT PRESSURE GRADIENT IN SAID HEAT EXCHANGER UNIT VARYING THE PROPORTION OF SAID FIRST PORTION WITH RESPECT TO SAID SECOND PORTION IN ACCORDANCE WITH THE INSTANTANEOUS CONTROL STATUS REQUIRED BY SAID HEAT EXCHANGER UNIT. 